The present invention relates to a process for producing N-acetylneuraminate lyase (hereinafter referred to as "NA lyase") using a microorganism constructed by recombinant DNA techniques.
NA lyase (EC 4.1.3.3) is the enzyme which catalyzes the conversion reaction of N-acetylneuraminate into N-acetyl-D-mannosamine and pyruvate.
It is known that the enzyme is used for the determination of a substance containing sialic acid in serum for diagnostic purposes. It is also known that the enzyme exists in an animal tissue, pathogenic microorganisms such as Clostridium perfringens, Vibrio cholerae, etc. and various nonpathogenic microorganisms. Only a little amount of the enzyme is produced by culturing these microorganisms in a medium which is usually used in an enzyme production.
It has been reported that the yield of the enzyme was enhanced by adding N-acetylneuraminate to the medium (Japanese Patent Publication Nos. 54153/81 and 51751/81).
The utilization of N-acetylneuraminate is economically disadvantageous and it is demanded to develop the process for producing NA lyase without utilization of N-acetylneuraminate.
As a result of studies made to develop such a process, it has been found that an NA lyase producing microorganism constructed by incorporating a hybrid plasmid into a recipient of the genus Escherichia produces NA lyase in a high yield in a medium which does not contain N-acetylneuraminate.